A Barnacle Attaches for Life (Yes, They're Living Crustaceans)

If you live near or have ever visited the coast, you've probably seen barnacles. But how much do you actually know about these sea creatures? Laszlo Podor / Getty Images

Ever notice those little crusty clumps stuck to rocks, boat hulls or even whales? Those are barnacles, and while they might not look like much, they're marvels of the natural world.

These tiny creatures are crustaceans, closely related to crabs and lobsters, and they’ve evolved some wild adaptations for life in the intertidal zone. Barnacles attach to a surface once and stay put for life.

Most barnacles, especially the acorn and gooseneck varieties, start life as barnacle larvae drifting in the ocean before transforming into juvenile barnacles and settling down on a hard surface.

How Barnacles Live and Feed

Barnacles live in shallow waters, usually in the intertidal zone where the ocean meets land. Adult barnacles encase themselves in six calcium plates that form a protective shell.

When the tide comes in, the barnacle opens up, extending its feathery appendages — called cirri — to sweep plankton and detritus from the water. These thoracic limbs act like tiny combs or fans, making barnacles efficient filter feeders.

clams with barnacles — These tiny barnacles made themselves at home on shellfish.
Jacky Parker Photography / Getty Images

When the tide goes out, the barnacle closes its shell tight to conserve moisture and avoid predators like some species of crabs, snails and mussels. It’s a low-key but effective strategy for surviving in a zone where drying out is just as dangerous as being eaten.

The Weird Barnacle Life Cycle

The barnacle life cycle includes two larval stages: the nauplius and the cyprid. After fertilized eggs hatch, the nauplius larvae go through six molts before becoming cyprid larvae.

The cyprid doesn’t eat; its job is to find a perfect surface — rocks, pilings, even ships or whales — to call home. Once it finds a spot, it uses special cement glands to permanently glue itself in place.

From there, it transforms into an adult barnacle, complete with hard shells and cirri. Most barnacles are hermaphroditic, meaning one barnacle can produce both eggs and sperm. Since barnacles can't move, they extend long reproductive organs to fertilize neighboring members of the same species.

Where Barnacles Cause Trouble

While barnacles are cool, they can also be a nuisance. Their habit of attaching to ships causes biofouling, which increases drag and fuel consumption.

More fuel means higher costs for shipping and more emissions. That’s why antifouling paints and coatings are big business in the marine industry.

Some motorists have even mistaken clusters of barnacles for damage on their hulls — a salty surprise if there ever was one. Even whale skin can become a habitat, turning one barnacle into a globe-trotting hitchhiker.

What Eats Barnacles?

Despite their hard exterior, barnacles aren’t invincible. Other sea life — including some species of snails, crabs, and even fish, can pry open or scrape off barnacles to get to the soft body inside.

Humans in some cultures eat gooseneck barnacles, considered a delicacy. And way back in the day, people believed geese hatched from barnacles (a misconception that came from seeing goose barnacles on driftwood).

Today, we know better thanks to advancements in brain and marine sciences. But barnacles still remind us that even small, overlooked creatures play big roles in sea life ecosystems.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.